| 词条 | Junkers Ju 252 | ||||||||||||||||||
| 释义 |
The Junkers Ju 252 was a German cargo aircraft that made its first flight in late October 1941. The aircraft was planned as a replacement for the Junkers Ju 52/3m in commercial airline service, but only a small number were built as cargo aircraft for the Luftwaffe. Design and developmentThe original Ju 252 came about after talks between Junkers and Deutsche Lufthansa in December 1938. Lufthansa requested a new design that would replace the Ju 52, but offer much greater loads, seating, range and performance. Junkers responded with the EF.77 design with a pressurized fuselage with seating for up to 35, making it one of the larger airliners in the world at that time. It was powered by three Junkers Jumo 211F engines, in nacelles almost identical in appearance, each complete with annular radiator and possibly as Kraftei unitized "power-egg" modular engine installations, to those on Jumo 211-powered versions of the Junkers Ju 88, replacing the BMW 132 of the Ju 52, which dramatically improved performance. Compared to the Ju 52, the Ju 252 was twice as heavy (13,100 kg vs. 5,600), was over 100 km/h faster (440 km/h vs. 305), and had dramatically improved range (3980 km vs. 1300) when fully loaded. Design was headed by Konrad Eicholtz.[1] By the time the prototype was ready to fly in October 1941, the war was already in progress and the Luftwaffe took over development. Like earlier tail-dragger designs, the Ju 252 would normally be difficult to load when parked, owing to the sloping floor. Junkers had already pioneered - with the earlier Junkers Ju 90's fifth and sixth prototype airframes during 1939 - a unique solution to this problem, the Trapoklappe, a hydraulically powered ventral rear loading ramp that possessed powerful enough operating mechanisms to lift the plane off its tailwheel, leveling the floor and allowing oversized cargo to be loaded directly forward into the fuselage. Even though cargo aircraft of all nations since World War II have used nosewheel landing gear undercarriage designs, the Trapoklappe concept of a rear loading ramp that forms the opening rear ventral panel of the fuselage of a cargo aircraft, is a ubiquitous feature of most military airlift cargo aircraft to the present day. Although the Ju 252 was a vast improvement over the Junkers Ju 52/3m, the situation at that time did not permit any disruption of the existing production lines, and the Reich Air Ministry (RLM) was of the opinion that any replacement for the Junkers Ju 52/3m must make minimum demands on supplies of strategic materials and use power plants not required by combat aircraft. Junkers was then instructed to investigate the possibility of redesigning the Ju 252 in order that a considerable portion of wood could be included in its structure, simultaneously replacing the Junkers Jumo 211F engine with the BMW Bramo 323R engine of which surplus stocks existed. The result was the Junkers Ju 352. Production of the Ju 252 was restricted to already completed prototypes plus those for which major assemblies had already been semi-completed, thus only fifteen transports of this type were completed before production was switched to the Junkers Ju 352. Specifications (Ju 252A){{aircraft specifications|plane or copter?=plane |jet or prop?=prop |ref=Warplanes of the Third Reich[2] |crew=3-4 |capacity= |payload main= |payload alt= |length main=25.11 m |length alt=82 ft 4¼ in |span main=34.10 m |span alt=111 ft 10⅛ in |height main=5.75 m |height alt=18 ft 10⅓ in |area main=122.6 m² |area alt=1,320 ft² |airfoil= |empty weight main=13,127 kg |empty weight alt=28,880 lb |loaded weight main=22,257 kg |loaded weight alt=49,560 |useful load main= |useful load alt= |max takeoff weight main=24,050 kg |max takeoff weight alt=52,911 lb |max takeoff weight more=(overload) |more general= |engine (prop)=Junkers Jumo 211F |type of prop=liquid-cooled inverted V12 engines |number of props=3 |power main=1,007 kW |power alt=1,350 hp |power original= |max speed main=438 km/h |max speed alt=237 knots, 272 mph |max speed more=at 5,800 m (19,030 ft) |cruise speed main=335 km/h |cruise speed alt=181 knots, 208 mph |cruise speed more=(econ cruise) |stall speed main= |stall speed alt= |never exceed speed main= |never exceed speed alt= |range main=3,981 km |range alt=2,150 nmi, 2,473 mi |range more=with maximum payload, 6,600 km (3,565 nmi, 4,100 mi) with 2,000 kg (4,400 lb ) payload |ceiling main=6,300 m |ceiling alt=20,670 ft |climb rate main=12.5 m/s |climb rate alt=748 ft/min |loading main= |loading alt= |thrust/weight= |power/mass main= |power/mass alt= |more performance= |guns=
|avionics= }} See also{{Aircontent||related=
|similar aircraft= |sequence= |lists=
|see also= }} Notes1. ^{{cite web|url=http://www.geocities.com/hjunkers/ju_who_e.htm |title=Junkers – Who is Who? E |accessdate=2016-06-22 |last=Zoeller |first=Horst |coauthors= |date= |format= |work= |publisher=The Hugo Junkers Homepage |pages= |quote= |deadurl=unfit |archiveurl=https://web.archive.org/web/20091027072816/http://www.geocities.com/hjunkers/ju_who_e.htm |archivedate=October 27, 2009 }} 2. ^Green 1972, p. 493. References
External links{{commons category|Junkers}}
6 : German military transport aircraft 1940–1949|World War II transport aircraft of Germany|Junkers aircraft|Trimotors|Low-wing aircraft|Aircraft first flown in 1942 |
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